Retinopathy of prematurity (ROP) is a leading cause of blindness in children. The disease can be successfully treated with retinal laser surgery, but detection involves subjecting at-risk infants to physically stressful, resource-intensive and thereby costly, serial diagnostic eye exams. Risk of ROP is currently defined primarily only by birth weight and gestational age cut-points, but these criteria are not efficient for identifying severe ROP. In the US, in 2006 alone, an estimated 65,000 babies underwent eye exams, but less than 5% of infants examined required laser surgery. Nevertheless, because of the serious consequences of missing a potential case of blindness, the protocol must maintain high sensitivity, even at the cost of repeatedly examining children who never require treatment, many of whom never develop retinopathy. The overall goal of this project is to develop a ROP prognostic model that incorporates postnatal growth measurements with birth weight and gestational age in order to greatly reduce the number of infants requiring exams in the US. Basic science and clinical research suggest that slow postnatal growth is predictive of severe ROP and more accurately identifies infants at risk for developing treatment-requiring ROP. The project specific aims are to (1) develop a prognostic model using postnatal weight gain to identify infants who are likely to develop severe ROP, (2) validate the model prospectively in a diverse cohort of at-risk infants, and (3) evaluate the relative cost-effectiveness of the prognostc model versus conventional ROP screening guidelines. The Growth-ROP (G-ROP) Collaborative Study Group consists of 19 geographically and racially diverse centers (18 US, 1 Canadian). The G-ROP group will conduct a retrospective study of 8,865 infants to develop the model and subsequently a prospective study of 4,000 infants to validate the model. Accomplishing the project specific aims may lead to a proposal for revision of current US ROP screening guidelines, with a potential to greatly reduce the screening burden in the US and identify early those infants who might benefit from preventive interventions being developed.